Antifogging combination of iso-ascorbic acid and 2 to 15 g. of hydroquinone



United States Patent Oflice 3,333,215 Patented May 14, 1968 3,383,215 ANTIFOGGING COMBINATION F ISU-ASCGRBTC ACID AND 2 T0 G. 0F HYDROQUINONE Albert Edward Harris and John Gough, llford, Essex,

England, assignors to Ilford Limited, iiford, Essex, England, a British company No Drawing. Filed July 9, 1964, Ser. No. 381,522 Claims priority, application Great Britain, July 19, 1963, 28,699/63 7 (Jlaims. (Cl. 96-1t)9) ABSTRACT OF THE DISCLOSURE There is provided a photographic material comprising a gelatino silver halide emulsion, suitable for being carried on a support such as paper, which contains from .1 to 1 gram per gram mol of silver present in the emulsion, a compound of the formulae:

where X is selected from the class consisting of (1 0, C=NH and CH-COOH and R is selected from the class consisting of hydrocarbon and hydroXyhydr-ocarbon residues, and 2 to 15 grams of hydroquinone. The emulsion provides a synergistically improved photographic material which essentially prevents spots forming in the developed emulsion, which spots are due to the sensitivity of the emulsions to metallic iron.

This invention relates to photographic materials and more particularly to such materials which comprise a support and one or more superimposed layers of gelatino silver halide emulsion. The support will usually be of film base or of paper carrying a White pigment layer, e.g. a baryta layer.

It has been observed over 'a period of many years that the vast majority of gelatino silver halide photographic emulsions are sensitive to metallic iron, such that iron particles present in the film base, in the paper or baryta coating, or in the emulsion, cause spots to be formed in the developed emulsion layer. Thus when a photographic material which contains iron particles is exposed and developed to a medium grey density, each iron particle will be seen to be surrounded by a halo of density different from the surrounding image. The actual area of the spot may be several hundred times that of the iron particle which causes it, and generally the effect is one of desensitisation of the emulsion. The spots may show up as white or dark and may have respectively dark or light halos, but are most frequently either white spots, or dark spots with a light halo.

Considerable research has been carried out in an effort to find a treatment for the photographic material which will minimise or even inhibit the formation of such spots. One method of achieving such results which has been found of some value is to include in one or more of the layers of a photographic material consisting of -a support, one or more layers of gelatino silver halide emulsion, and optionally other layers, a small amount of a compound of the general tautomeric Formulae I:

where X is one of the groupings o=o, and R is a hydrocarbon or hydroXy-hydrocarbon residue. The group R may be a phenyl group or a substituted phenyl group, such 'as a sulphophenyl or ha] ophenyl group, or other aryl or substituted aryl group, or an alkyl group or substituted alkyl group such as a hydroxyalkyl (erg. hydroxymethyl) group.

Specific compounds, or classes of compounds, of the foregoing formulae which may be employed are: ascorbic acid, isoascorbic acid, 4-aryl-2-oxytetronic acid and 4-aryl-2-oxytetronimide.

In these latter classes of compound the aryl group may be phenyl, i.e. 4-phenyl-2-oxytetronic acid or 4-phenyl-2 oxytetronimide or it may contain su-bstituents, examples of such compounds being 4-o-sulphophenyl-Z-oxytetronirnide, 4-o-chlorphenyl-Z-oxytetronimide and 4-0-chlorphenyl-Z-oxytetronic acid. Such compounds may be prepared by the method of Dahn et al., Helv. Chim. Acta, 37, 1309, 1318 (1954).

The said compounds may be included in or on the support (for example raw paper base) in a baryta layer, in a layer coated over a baryta layer, in the emulsion itself, or in a supercoat on the emulsion. Generally, about 0.1 to 1.0 g./litre of the coating medium in which they are applied constitutes a suitable proportion. However, the optimum proportions vary with the compounds and with their location. For example, using iso-ascorbic acid or l-ascorbic acid a range of 0.05 to 0.5 g./litre added to the photographic emulsion has been found suitable.

Most advantageously they should be employed in acid medium, e.g. at pH 4.5 to 6.0.

The said compounds, so used, have been found to reduce the incidence of spots caused by particles of iron present.

It has now been found that the effect of the compounds referred to above may be synergistically improved by the inclusion, with the said compound, of a small proportion of hydroquinone.

According to the present invention therefore there is provided a photographic material which comprises a support carrying one or more layers of gelatino sllver halide emulsion, at least one such layer being formed of a said emulsion which contains 0.1 to 1.0 grams per g. mol of silver of a compound of general Formula I and 2 to 15 grams per .g. mol of silver of hydroquinone.

In the preferred form of the invention the compound of general Formula I is iso-ascorbic acid.

The following example will serve to illustrate the invention:

EXAMPLE To a quantity of gelatino silver chlorobromide emulsion prepared for coating on a paper support and containing 1.0 g. mole of silver halide was added 0.33 g. of isoascorbic acid and 5 g. of hy-droquinone, the pH being adjusted to 5.0.

The emulsion was applied to baryta-coated paper base known to be contaminated with particulate iron, and dried. The resulting light-sensitive paper was exposed to light and developed. A comparison test was made using the same emulsion but omitting the hydroquinone. The formation of spots due to the iron contamination was found to be substantially less in the case where the emulsion contained hydroquinone as set forth.

Similar results were obtained using equal weights of l-ascorbic acid, 4-o-sulphophenyl-Z-oxytetronirnide, 4-0- chloro-phenyl-2-oxytetronimide, 4-phenyl 2 oxytetronimide and 4-phenyl-2-oxytetronic acid.

Optionally, and with advantage, there may be included in the emulsions of this invention a stabiliser known per se,

6 i ha RC X H OH where X is selected from the class consisting of and R is selected from the class consisting of hydrocarbon and hydroxyhydrocarbon residues, and 2 to 15 g. of hydroquinone.

2. A photographic material which comprises a support carrying at least one layer of a gelatino silver halide emulsion which contains, per gram mol of silver present in the emulsion, 0.1 to 1.0 g. of isoascorbic acid and 2 to 15 g. of hydroquinone.

3. A photographic material which comprises a support carrying at least one layer of a gelatino silver halide emulsion which contains, per gam mol of silver present in the emulsion, 0.1 to 1.0 g. of a compound of the tautomeric formulae:

0 OH l'; m B R-(JH where X is selected from the class consisting of C=O, C=NH and and R is selected from the class consisting of hydrocarbon and hydroxyhydrocarbon residues, and 2 to 15 g. of hydroquinone, and further contains an anti-foggant stabiliser.

4. A photographic material which comprises a support carrying at least one layer of a gelatino silver halide emulsion which contains, per gram mol of silver present in the emulsion, 0.1 to 1.0 g. of isoascorbic acid and 2 to 15 g. of hydroquinone, and further contains an anti-foggant stabiliser.

5. A photographic material which comprises a support carrying at least one layer of a gelatino silver halide emulsion which contains, per gram mol of silver present err-c0011 C=NH and CHCOOH and R is selected from the class consisting of hydrocarbon and hydroxyhydrocarbon residues, and 2 to 15 g. of hydroquinone, and further contains, as anti-foggant, 2-methylthio-5-hydroxy-7-methyl-1,3,4,7-tetraazaindene.

6. A photographic material which comprises a support carrying at least one layer of a gelatino silver halide emulsion which contains, per gram mol of silver present in the emulsion, 0.1 to 1.0 g. of isoascorbic acid and 2 to 15 g. of hydroquinone, and further contains, as anti-foggant, 2-methylthio-5-hydroxy-7-methyl-1,3,4,7-tetraazaindene.

7. A photographic material which comprises a support carrying at least one layer of a gelatino silver halide emulsion which contains, per gram mol of silver present in the emulsion, 0.1 to 1.0 g. of a compound of the tautomeric formulae:

where X is selected from the class consisting of and R is selected from the class consisting of hydrocarbon and hydroxyhydrocarbon residues, and 2 to 15 g. of hydroquinone, the pH of the emulsion being from 4.5 to 6.0.

CH-COOH References Cited UNITED STATES PATENTS NORMAN G. TORCHIN, Primary Examiner.

J. H. RAUBITSCHEK, R. E. MARTIN,

Assistant Examiners. 

